JEST stopped working with version 2.3.0

[LucaMele]

axa-ch-webhub-cloud/pattern-library#1452

axa-ch/jest-test-plib-v2#2

[AndyOGo]

Since 2.3.0 Jest throws TypeError: The custom element constructor's prototype is not an object.:

From my insights it seems that two different Object constructors are being used, which causes this check to fail.

polyfills/packages/custom-elements/src/CustomElementRegistry.js

Lines 168 to 173 in 75717f8

	try {
	/** @type {!Object} */
	const prototype = constructor.prototype;
	if (!(prototype instanceof Object)) {
	throw new TypeError('The custom element constructor\'s prototype is not an object.');
	}

Reproduction Repo with relevant analysis in PR description:
axa-ch/jest-test-plib-v2#1

Lock down to 2.2.10 to mitigate this type error:
axa-ch/jest-test-plib-v2#2

[tomstumshais]

Hey! Any progress with this issue?

[peabnuts123]

If you are using @webcomponents/custom-elements lock down to version ^1.2.4

[elisiondan]

If you don't actually need the customElements to return an actual element and you're only aiming to avoid this error, you can can mock the implementation.

Create a config file for jest that will be included in all tests as part of a setupFiles option.

setup-globals.js
window.customElements = {
  define: () => {},
};

// jest.config.js
  ....
  setupFiles: [
    '<rootDir>/YOUR-PATH/setup-globals.js',
  ],

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been automatically closed after being marked stale. If you're still facing this problem with the above solution, please comment and we'll reopen!